1. Field of the Invention
The present invention relates to a dialkyl dialkoxycarbonylphenylphosphonate, a production process therefor and a process for producing a dicarboxyphenylphosphonic acid.
2. Related Art
Only dimethyl 2,3-dimethoxycarbonylphenylphosphonate represented by the following formula (V) is known as a dialkyl dialkoxycarbonylphenylphosphonate. ##STR1## A process for producing this comprises obtaining 1,2-dimethoxycarbonyl-3-dimethoxyphosphonocyclohexa-1,4-diene as an intermediate through a Diels-Alder reaction between 1-(1,3-butadienyl)phosphonic acid and dimethyl acetylenedicarboxylate and aromatizing the obtained intermediate into dimethyl 2,3-dimethoxycarbonylphenyl phosphonate of interest using nitrobenzene and an activated carbon supported palladium catalyst. Although the Diels-Alder reaction is very interesting, it is not preferred and can not: be employed for the industrial-scale production of dimethyl 2,3-dimethoxycarbonylphenylphosphonate because of its low reaction yield (Journal of Organic Chemistry, vol.35, pp.1691, 19703.
Dialkyl monoalkoxycarbonylphenylphosphonates obtained by an Arbuzov reaction are known. A process for producing these comprises reacting a trialkyl phosphite with a monoalkoxy carbonylphenyl halide using nickel chloride as a catalyst at a reaction temperature of 150.degree. to 160.degree. C. Chem. Ber., vol.103, pp.2428, 1970, Chem. Rev. vol.81, pp.415, 1981 for the outline of the Arbuzov reaction!. However, there are unknown dialkyl dialkoxycarbonylphenylphosphonates produced by an Arbuzov reaction using a dialkoxycarbonylphenyl halide.
As a dicarboxyphenylphosphonic acid is known o-dicarboxyphenylphosphonic acid represented by the following formula (VI). ##STR2##
A process for producing this comprises reacting o-xylene with phosphorus pentaoxide in an autoclave at a temperature of 270.degree. C., reacting phosphorus oxychloride and phosphorus pentaoxide with the reaction product from which unreacted o-xylene has been removed to obtain o-dimethylphenylphosphonyl dichloride (isomer mixture). This o-dimethylphenylphosphonyl dichloride is chlorinated by exposure to ultraviolet light to obtain a chlorinated product thereof. An aqueous solution of potassium hydroxide is: added to this chlorinated product to oxidize it while the reaction solution is maintained alkaline by an aqueous solution of potassium hydroxide and an aqueous solution of potassium permanganate, whereby o-dicarboxylphenylphosphonic acid is obtained refer to the disclosure of U.S. Pat. No. 2,834,804!.
However, it cannot be said that this process is a practical production process because the obtained o-dicarboxyphenylphosphonic acid is an isomer mixture, potassium permanganate must be treated after completion of the reaction, and special reaction devices such as a high-temperature and high pressure autoclave and a photochemical reaction device are required.
There is known a process for producing a substituted phenylphosphonic acid by hydrolyzing a dialkyl monoalkoxycarbonylphenylphosphonate obtained by an Arbuzov reaction with hydrochloric acid Chem. Ber. vol.103, pp.2428, 1970!. However, there is unknown a process for producing a dicarboxyphenylphosphonic acid by hydrolyzing a dialkyl dialkoxycarbonylphenylphosphonate through an Arbuzov reaction using a dialkoxycarbonylphenyl halide.
The inventors of the present invention have paid attention to dialkyl dialkoxycarbonylphenylphosphonates which are useful as a resin modifier and have conducted intensive studies on dialkyl dialkoxycarbonylphenylphosphonates and a production process therefor. As a result, they have synthesized a novel dialkyl dialkoxycarbonylphenylphosphonate and have found a process for producing a dialkyl dialkoxycarbonylphenylphosphonate and a dicarboxyphenylphosphonic acid in high yield at a low cost. Thus, they have accomplished the present invention.
In the present invention, it has been found that a supported catalyst is excellent in yield and recovery as a catalyst.